Staying on top of search engine optimization requires time and effort that many small businesses can’t afford in-house. One obvious solution is to turn to an agency. But which ones can be trusted and which will under deliver and overcharge? Before just picking the number one result in a Google search for “SEO,” make sure to investigate the agency.

Hint: Cost is only a small part of the equation. It doesn’t matter how much you pay an agency of the don’t deliver what your site needs.

I’ve worked on both sides of the SEO equation: as senior SEO manager at Covario, an award-winning search agency, and now as the in-house SEO manager at Groupon, the leader in daily deals. From my experience, these 10 tips will help guide the SEO selection process.